The present invention deals with devices for heart stimulation, specifically, implantable defibrillator/pacemakers. In particular, the invention deals with electrode configurations for tripolar stimulation, designed to improve the stimulation characteristics.
Large amounts of research have been performed in the area of devices for providing appropriate cardiac stimulation. Such research has resulted in sophisticated technologies for efficient and reliable delivery of stimulation pulses, namely, implantable defibrillator/pacemakers. There are many such devices known in the prior art.
Among the more recent devices are those designed for bi-atrial pacing, in which sensing and stimulation of both the right and left atria is performed. Such an arrangement is particularly useful in patients having unhealthy atrial delays.
References in the literature that deal with earlier questions relating to bi-atrial stimulation and its precursors include:
1. Prakash, A., et al., xe2x80x9cPrediction of outcome of chronic single and dual site right atrial pacing for atrial fibrillation prevention by acute electrophysiologic testing,xe2x80x9d PACE, Vol. 20, Part II, April 1997, Abstract No. 97.
2. Belham, M., et al., xe2x80x9cBi-atrial pacing for atrial fibrillation: where is the optimal site for left atrial pacing,xe2x80x9d PACE, Vol. 20, Part II, April 1997, Abstract No. 98.
3. Delfaut, P., et al., xe2x80x9cContinuous overdrive pacing prevents recurrent atrial fibrillation during single and dual site right atrial pacing,xe2x80x9d PACE, Vol. 20, Part II, April 1997, Abstract No. 99.
4. Prakash, A., et al., xe2x80x9cMulticenter experience with single and dual site right atrial pacing in refractory atrial fibrillation,xe2x80x9d PACE, Vol. 20, Part II, April 1997, Abstract No. 100.
These references, among many others in the literature, demonstrate the advantages of pacing the atrium from both the right atrium, usually from the atrial appendage, and the left atrium, from the coronary ostium, in preventing the onset of atrial fibrillation.
In addition to bi-atrial stimulation, bi-ventricular stimulation has also been used, particularly in assisting the left ventricle in patients having congestive heart failure.
Prior-art bi-atrial and bi-ventricular pacing have been performed using either:
1. two unipolar (cathodal) electrodes, in the atrium or ventricle (typically, a tip electrode buried in the myocardium) and in the coronary sinus (CS) (floating in the coronary sinus ostium for bi-atrial or in the great cardiac vein for bi-ventricular), with the pacemaker housing used as the reference;
2. two unipolar electrodes (cross-chamber bipolar stimulation), with an atrial/ventricular tip electrode acting as a cathode and a CS ring electrode acting as an anode, or the reverse; or
3. two bipolar sets of electrodes in the atrium/ventricle and in the CS/great cardiac vein.
It is an object of the invention to provide a defibrillator/pacemaker device providing performance superior to prior-art devices.
It is a further object of the invention to implement such a device in a simple, cost-effective manner.
These and other objects of the invention are achieved by the use of tripolar stimulation with a particular electrode configuration. Tripolar stimulation provides the following advantages, respectively, over the above-mentioned prior-art alternatives:
1. Tripolar stimulation exhibits significantly lower impedance at the cost of only a slightly higher pacing threshold;
2. Tripolar stimulation exhibits a much lower pacing threshold, but with greater impedance; however, it should be noted that the threshold in cross-chamber bipolar stimulation is typically so high that the device has no margin left; and
3. Tripolar stimulation has a slightly higher impedance while maintaining the same pacing threshold.
(Note that, in general, higher impedance and lower pacing threshold are desirable, for improved efficiency in pulse delivery/power consumption.)
In particular, the invention is directed toward implanting a heart stimulation device (i.e., pacemaker/defibrillator) for tripolar stimulation. Along with the device, electrodes are implanted in the heart such that electrodes in a heart chamber (i.e., atrium or ventricle) and in a blood conduit to the heart (e.g., the CS or great cardiac vein) have one polarity (i.e., positive [anode] or negative [cathode]) for delivering stimulation pulses, while one or more additional electrodes in the heart chamber have the opposite polarity.
The invention may be used for either bi-atrial or bi-ventricular stimulation, and it can also be extended to dual-site atrial/ventricular stimulation.
In a first embodiment of the invention, a method of implementing tripolar cardiac stimulation in a heart comprises steps of:
(a) implanting a cardiac stimulation device having anodic and cathodic connections and including means for providing electrical stimulation pulses through said anodic and cathodic connections;
(b) electrically connecting first and second electrode lines to respective ones of the anodic and cathodic connections;
(c) electrically coupling at least two electrodes to one of the electrode lines;
(d) electrically coupling at least one electrode to the other electrode line; and
(e) implanting at least one of the at least two electrodes electrically coupled to the one electrode line and the at least one electrode electrically coupled to the other electrode line in a heart chamber; and
(f) implanting at least one other of the at least two electrodes electrically coupled to the one electrode line in a blood vessel of the heart.
In a second embodiment of the invention, a method of implementing tripolar cardiac stimulation in a heart comprises steps of:
(a) implanting a cardiac stimulation device having anodic and cathodic connections and including means for providing electrical stimulation pulses through said anodic and cathodic connections;
(b) electrically connecting first and second electrode lines to respective ones of said anodic and cathodic connections;
(c) electrically coupling at least two electrodes to one of said electrode lines; and
(d) electrically coupling at least one electrode to the other one of said electrode lines; and
(e) implanting said electrodes in a single heart chamber.